CHIRPED DICHROIC MIRROR AND A SOURCE FOR BROADBAND LIGHT PULSES

摘要

The present invention is directed to a chirped dichroic mirror comprising a stack of alternating high refractive index and low refractive index layers, a front end portion including an antireflective coating followed by an impedance matching region in which the ratio of the optical thickness of a high refractive index layer to the optical thickness of the next following low refractive index layer is adiabatically increasing to a first value, the impedance matching region being followed by a chirped mirror region where the Bragg wavelength of the layer pair is generally increasing or generally decreasing, characterized in that the layers in a back end region form a second impedance matching region in which the ratio of the optical thickness of a high refractive index layer to the optical thickness of the next following low refractive index layer starts at the value of this ratio in the adjacent chirped mirror region and is then adiabatically decreasing in order to provide matched impedance to the surrounding medium over the transmission spectral band.

主权项

1. A chirped dichroic mirror comprising:
a stack of alternating high refractive index and low refractive index layers, each of said layers presenting an optical thickness, each of said high refractive index layers and the next following low refractive index layer forming a layer pair, each of said layer pairs defining an optical thickness ratio of the optical thickness of the high refractive index layer to the optical thickness of the low refractive index layer, each of said layer pairs presenting a Bragg wavelength, said mirror defining a front end portion including an antireflective coating followed by an impedance matching region in which the optical thickness ratio is adiabatically increasing to a first value, said mirror defining a chirped mirror region following the impedance matching region, where the Bragg wavelength of the layer pairs is generally increasing or generally decreasing in the chirped mirror region, said mirror defining a back end region following the chirped mirror region, the optical thickness ratio having a chirped mirror region value at an end of the chirped mirror region adjacent the back end region, the layers in the back end region forming a second impedance matching region in which the optical thickness ratio starts at the chirped mirror region value and is then adiabatically decreasing, the back end region thereby configured to provide matched impedance to a surrounding medium over a transmission spectral band.